The placement of medicinal liquid into a patient's eye tends not only to be difficult but wasteful. The eye dropper bottles and tips on the market today produce a large drop and often more than one drop spontaneously falls from the dropper bottle either into the eye or onto the skin of the face and eyelids. This not only creates a waste of drops, but can be irritating to the skin and eye.
This invention creates a small droplet that falls from the free end of the tip rather than migrating along the outer surface of the stem of the dropper. The accumulation of liquid along the outer stem surface of a conventional dropper tip, when held in a near horizontal orientation, will tend to produce a larger and larger drop as liquid is expressed from the reservoir until the force of gravity overcomes the surface tension and causes the drop to fall. The drop created by the tip according to the method of this invention is much smaller and more consistent in size, falls freely from the distal end of the tip and is more easily instilled into the eye.
The creation of a very small drop is important in the treatment of various ocular conditions, but it is especially important in the treatment of Keratitis Sicca or “dry eye.” Millions of people suffer from some type of tear dysfunction. Many individuals do not make an adequate amount of tears and thus the eye may have symptoms of burning, irritation or sandy feeling, itching, and even a decrease in visual acuity since the tear film is responsible for maintaining good vision.
The normal tear film over the eye consists of three layers: an outer lipid or oily layer, a middle aqueous or watery layer and an inner layer of mucin that holds the rest of the tear film to the cornea and outer structures of the eye. The tear volume in a normal healthy eye is estimated to be about six microliters, a microliter being 1/1,000,000th of a liter. The size of a drop from a conventional eye dropper on the market today ranges from approximately fifty to sixty microliters, some eight or more times the normal volume of tear in the eye. A mini drop instilled into an eye that is only twelve microliters (some two times the tear volume) would provide much more benefit to the eye compared to the flushing and washing action of too much liquid. Since the drop produced is very small, it would greatly reduce the need for the use of tissues to dry excess liquid from the eyelids and skin. This would spare the lipids that are necessary along the eyelid margins.
Presently there are dozens of artificial tears on the market that can be purchased over the counter. Most of them not only produce a large drop for the eye, but the directions on the bottle suggest that more than one drop may be used. This sudden excess of moisture that is instilled into the eye at one time may be more harmful than beneficial if it irrigates away the mucin, lipid layer and proteins of the tear film. Also, when an excess of medicinal drop is used, the patient wipes the eye profusely with tissue or cloth and thereby risks the removal of the beneficial lipids that are produced by the oil glands of the eyelids.
If artificial tears are instilled into an eye too frequently, there is the fear of washing out the more beneficial components of the tear film, such as the mucin layer, the lipid layer and other elements. Most artificial tears are designed to replace the aqueous or watery portion of the tear film. Thus, if a very small droplet is created for instillation, a person may use drops more frequently and still preserve the beneficial components of the tear film that the eye naturally produces. More frequent and smaller drops may help repair the dehydrated cells of the cornea and conjunctiva, along with providing more comfort to the eye. If a smaller droplet is used in the eye, the patient will have much less need for wiping off the excess medication from the eye and eyelids and thus preserve the lipid that is secreted by the oil glands that open onto the marginal surface of the eyelids. The repeated use of tissues for removing the excess medication from the eye and eyelids may be dehydrating and counter productive to the treatment of the dry eye.
It can be shown that when a regular size drop from a conventional eye dropper is instilled into the eye, an excess of liquid flows onto the eyelashes and skin of the face. This liquid dries and can be observed under the biomicroscope to produce numerous flakes of dried liquid that are formed and adhere to the skin of the face and eyelids. These dried flakes of medication on the skin of the eyelids can form up to one-half inch away from the lower eyelid margin. When the dry eye is treated with eye drops four or five times a day, one can readily see the problem of irritation to the skin and eyelids from these dried particles.
Contact lens wearers often have symptoms of dryness of the eyes, especially when the lenses are worn for longer periods of time or in certain situations where dehydration of the eye occurs. Medicated drops and artificial tears have been designed to help alleviate the symptoms that come from these conditions and may be instilled as needed. When a large drop or drops are instilled into an eye with a patient wearing contact lenses, there is a tendency for this large volume to “float” the lens and can cause it to slide off the cornea where it must remain for good visual acuity. However, when a mini drop is instilled into an eye with a contact lens, the small amount of liquid is beneficial for the relieving of the symptoms and yet much less likely to cause the lens to move out of its proper place. Also, since the volume is very small, drops may be used more often and without the problems that come from excessive moisture.
There are numerous other applications for the use of a very small drop in various eye conditions and diseases. One example is that certain anti-glaucoma medications have the side effect of causing eyelashes to grow and thicken. If a smaller amount of drop is instilled into an eye, there will be much less chance of coating the eyelashes and the eyelids and thus reducing this side effect. Also, less medication on the eyelids reduces the irritation and allergy that is often seen with medications that are frequently used in the eyes.
A smaller drop is more desirable when using various drops for testing purposes. An example is when a person is being tested for glaucoma. Applanation tonometry is the most common method used to test for intraocular pressure. It is necessary to use a drop containing sodium fluorscein and a topical anesthetic to do this test. The conventional bottles that contain these ingredients for testing purposes will form a drop that is three to four times the volume of the mini drop produced by the present invention. This volume from the mini drop tip, even though much smaller, is still adequate to perform the test easily and successfully. The advantages are two-fold. First, much less drop is used and therefore a savings in cost is provided. However, the greater advantage is that the patient is not left with an excess of yellow dye in the eye and on the eyelids when the test is completed. Patients are much happier without this side effect as they leave the examining room. By using a smaller amount of dye when testing for glaucoma, abnormal stain patterns may be seen with the biomicroscope that would otherwise be covered up with the large amount of fluid in the eye that comes from conventional dropper tips.
Most standard eye droppers are described in the prior art as somewhat conically-shaped with a larger base end of the tip attached to a reservoir of liquid eye medication. The free end of the tip is penetrated by an opening through which each drop of liquid eye medication is discharged. With the distal end of a standard tip directed downward, an eye drop will likely fall from the opening in the tip toward a point on the patient's eye directly below the opening of the tip.
As the tip is rotated from an inverted position toward a more horizontal position, liquid flowing out the opening of the standard tip will have a tendency to spread over and wettably adhere to a portion of the exterior surface of the tip. Once the exterior surface of the tip becomes wetted by the liquid medication, each drop of liquid exiting the opening in the tip will flow along the wetted surface to accumulate at a point adjacent the boundary between the wetted and dry portion of the tip. As the discharged liquid flows to this boundary, sufficient mass will accumulate until a drop falls from a point adjacent the boundary. Consequently, the drop no longer falls from the end of the tip. Although a patient may have the end of the prior tip located directly above the eye, the drop will likely roll down the tip to release at a point away from the end of the tip and miss the eye altogether.
Accordingly, a need exists to make a dropper tip for eye drops or other mini drops that consistently creates a small droplet that falls freely from the distal portion of the tip rather than adhering to the outer surface of the stem of the tip. Such a dropper tip should be made of a soft, supple material rather than a rigid material in order to reduce any harm that might come from an accidental touching of the external structures of the eye.